#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<math.h>
int main()
{
	int sign = 1;
	double pi = 0.0;
	double n = 1.0;
	double term = 1.0;
	while (fabs(term) > 1e-6)
	{
		pi += term;
		n += 2;
		sign = -sign;
		term = sign / n;

	}
	pi = pi * 4;
	printf("pi=%10.8f\n", pi);
	return 0;
}